This invention relates to a device for connecting a pneumatic or hydraulic tool to a coupling, linking it with a liquid- or gaseous-fluid feed line; a fitting designed to cushion the pulsations, vibrations and mechanical shocks of percussion tools; and a method for cushioning or absorbing pulsations, vibrations and mechanical shocks in the operation of pneumatic or hydraulic percussion and/or vibrating tools.
Fittings are used in conjunction with couplings which serve as detachable interconnecting elements between rigid pipes and flexible conduits for fluids, i.e. liquid or gaseous substances, especially compressed air. Pneumatic or hydraulic tools such as impact, percussion or vibrating tools which are driven by pneumatic or hydraulic fluids such as compressed air, are connected to and disconnected from their respective feed lines via the aforementioned intermediate couplings. Examples of compressed-air-driven tools include road-construction equipment or pneumatic tools for tightening and/or removing automobile wheel nuts and studs etc., in all cases involving the transfer of strong vibrational forces, pulsating or hammering action from the percussion tool by way of the rigid connecting line to the coupling in which coupling the fitting is securely fastened. A contact surface of the fitting protrudes into a mating port in the coupling where it can be releasably locked in position either via a screw-collar or bayonet-type clamp or by a swivel or twist-lock mechanism in the coupling.
The manufacturers of quick-connect couplings and fittings take for granted that the users view these couplings and fittings merely as connectors subject to wear and tear and, hence, to periodic replacement. Their useful lifespan is limited as a function of the product and material quality, and the user still reviews only the cost/benefit ratio of his investment in couplings and fittings. Yet our experience in the most diverse fields of application of couplings and fittings has provided ample evidence to the effect that connectors of this type are predominantly used for feeding compressed air to pneumatic tools and frequently so-called vibrating screwdrivers, wrenches and hammers. The associated above-average wear, however, is ignored by the typical user until the coupling fails to function. In most cases, such failure exhibits itself in that detachable couplings come apart by themselves, whereby the two connecting elements, for instance a coupling and a fitting in the case of a flexible conduit, become uncontrollable, separating with a so-called whiplash effect as a result of the sudden compressed-air blowout and flying off with a corresponding velocity. This has led to accidents with the gravest consequences for those directly involved, for which the manufacturers of the couplings and fittings as well may be held liable.
At this juncture, work with compressed air is the subject of certain national and international regulations whereby a coupling must meet specific safety standards in terms of its connecting and disconnecting properties before it can be marketed as a so-called safety coupling. There is no comparable regulation, however, regarding the physical design of such connectors especially with respect to technical provisions aimed at preventing premature wear and tear of the locking elements which easily goes unnoticed by the non-expert.
Prior art has attempted to address this problem by interpositioning between the fitting and the connecting port on the tool a flexible tube section, but the configuration of the flexible conduit and its attachment to the fitting and, respectively, to the tool port turned out to be so complex and costly that this approach never really materialized.
There has also been a two-part fitting with an elastic, shock-attenuating intermediate layer which elastic layer is surrounded by a sleeve shrunk onto the elastomer material for generating radial inward pressure. In practice, this design has quickly led to fatigue or embrittlement of the elastomer material, causing the fitting to break apart.
Then there is Swiss patent CH 518.481 which describes an anti-vibration device intended to cushion the pulsations in a fluid-transmitting line. That document refers to the attenuation of pulsations in liquid-carrying lines which again fails to provide a suitable solution for a fitting or junction that connects a fluid line to a tool. Besides, the document describes a stepped through-hole which is hardly desirable in a fluid line.
It is therefore the objective of this invention to introduce a system by means of which the aforementioned pulsations, vibrations and hammering action are cushioned or absorbed so as not to be transferred to the interconnecting coupling, causing the fitting to break out of the coupling.
Specifically, the invention is aimed at providing a so-called xe2x80x9canti-vibration fittingxe2x80x9d whose basic physical design is such as to allow the transfer to the coupling of either none or only highly cushioned movements from the percussion- or vibration-type compressed-air tool. In the absence of vibrations or percussions at the coupling, the locking elements of the coupling are not constantly exposed to excessive shock loads and thus to extraordinary wear which would normally be noticed only after the connection, presumed by the user to be safe, starts to leak or even comes apart.
The device proposed is a so-called nipple-type fitting which serves to connect a pneumatic or hydraulic tool, especially for instance a percussion or vibration tool, to a coupling which links it with a liquid- or gaseous-fluid-carrying feeder or supply line, whereby the said device or fitting incorporates at least one first part with a protruding contact section which can be inserted or plugged into and thus releasably connected to a mating port in the coupling. A second part, incorporating a connector section, is so designed and provided as to permit solid connection to and with the tool. Both parts include at least one additional section each whereby the additional section of one part radially surrounds that of the other part with a space in between and an elastic junction is provided in that space between the two sections, which junction is produced by casting, injection-molding, extruding and/or, where appropriate, by reactive cross-linking or by vulcanizing an elastic, rubber-like material or thermosetting an elastic polymer between the two additional sections.
The device introduced by this invention is particularly suitable as a so-called anti-vibration fitting for connecting percussion tools such as pneumatic tools to quick-connect couplings. An anti-vibration fitting of this type essentially consists of two metal parts where one part is designed to attach firmly to the percussion tool while the other metal part, nipple-shaped, is so designed that it can be inserted and locked in the quick-connect coupling. Interpositioned between the two metal parts is a layer of an elastomer material or a vulcanized rubber serving to absorb or cushion vibrations or pulsations originating from the percussion tool. By predefining a specific Shore hardness the degree of attenuation between the percussion tool and the quick-connect coupling can be selected.
The anti-vibration fitting described above extends the life of the unions since the locking elements are exposed to a certain impact only when being connected or disconnected, which is tantamount to normal wear. The fitting described is generally suitable for all and any existing union and coupling systems since the nipple end of the fitting can be adapted to whatever connecting system is employed.
In producing the device per this invention, or anti-vibration fitting just described, it is possible to provide each of the two metal parts with a cylindrical or sleeve-type section, with one sleeve-type section radially enveloping the other section. The space left between the two sleeve-type sections can now be filled with the elastomer material or rubber which is introduced by casting or injection-molding and which, if desired, can then be vulcanized to a particular Shore hardness. Alternatively, the inner sleeve-type or cylindrical section can be jacketed with the elastomer material or rubber by the extrusion method, after which the other section is slipped over it. In this case as well it is possible, where appropriate, either by heat-treating or by other suitable measures to produce a partial cross-linking or vulcanization effect in the elastomer or rubber material for arriving at a particular Shore hardness.